Segmented Protective Tape for Uniform Lithium Doping in Compact Electrochemical Devices
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Solution Overview
Problem
As electrochemical devices, such as lithium ion capacitors, shrink in size, the protective tape used to prevent lithium deposition and shield lithium ions during pre-doping becomes a barrier, leading to non-uniform doping of lithium ions into the negative electrode.
Innovation Solution
The design incorporates a specific configuration of protective tapes around the negative and positive electrodes, ensuring the first protective tape covers the negative-electrode terminal and active material layer, and the second tape covers the positive-electrode terminal, with their combined widths being less than the circumference of the circle defined by the distance between the terminals, allowing lithium ions to pass through uniformly during pre-doping.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If protective tape is used to prevent lithium deposition and shield lithium ions during pre-doping, then the terminal is protected from direct contact with separators and lithium deposition is suppressed, but lithium ions are shielded and cannot be uniformly doped into the negative electrode
Solution Approach 1:
The protective tape is divided into multiple segments along the winding direction, creating gaps between segments that allow lithium ions to pass through during pre-doping while still providing protection against direct contact between terminals and separators. The segmented structure resolves the contradiction by maintaining terminal protection functionality while enabling uniform lithium ion distribution.
Solution Approach 2:
The protective tape has different properties in different regions: it provides continuous coverage in the radial direction to prevent terminal contact, but has discontinuous gaps in the winding direction to allow lithium ion penetration. This local differentiation of protective quality resolves the contradiction between protection and uniform doping.
2Volume of moving object
If the electrochemical device is made smaller to reduce size, then device compactness is improved, but the protective tape becomes a more significant barrier to lithium ion diffusion
Solution Approach 1:
By segmenting the protective tape in the winding direction, the patent creates multiple pathways for lithium ion diffusion. This segmentation ensures that even in compact devices where the tape represents a larger relative barrier, lithium ions can still penetrate uniformly through the gaps between segments, resolving the size-related doping uniformity issue.
Solution Approach 2:
The protective tape structure utilizes both radial and circumferential dimensions: continuous in the radial direction for protection, discontinuous in the circumferential direction for ion penetration. This dimensional approach allows the device to be compact while maintaining uniform lithium ion distribution despite the presence of protective tape.
3Object-affected harmful factors
If protective tape covers the terminal and active material layer, then direct contact between separators and terminal is prevented, but lithium ions are blocked from reaching the negative electrode uniformly
Solution Approach 1:
The protective tape is segmented in the winding direction with gaps between segments. This segmentation allows lithium ions to pass through the protective tape structure uniformly while the tape segments continue to prevent direct contact between separators and terminals, resolving the contradiction between protection and doping uniformity.
Solution Approach 2:
The segmented protective tape acts as an intermediary structure that mediates between the need for terminal protection and the need for uniform lithium ion access. The gaps between segments serve as channels for ion transport while the tape segments maintain the protective function.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This configuration ensures that lithium ions are uniformly doped into the negative electrode even when the device is compact, with the first distance between terminals being 8 mm or less and the outer diameter of the winding structure being 30 mm or less, preventing shielding by the tapes and ensuring uniform distribution.
Implementation Method 1
lithium ions are pre-doped into a negative electrode before use... as lithium ions elute into the electrolyte, those lithium ions are doped into the negative electrode
Data Source
AI summary
In an embodiment, an electrochemical device includes a winding structure which has a negative electrode, a positive electrode, and separators stacked and wound together; a negative-electrode terminal; a positive-electrode terminal; a first protective tape which covers the negative-electrode terminal and a negative-electrode active material layer; a second protective tape which covers the positive-electrode terminal and a positive-electrode active material layer; and electrolyte, wherein the positive-electrode terminal is separated from the negative-electrode terminal by a first distance. The width corresponding to the sum of a first width of the first protective tape along a winding direction of the winding structure, and a second width of the second protective tape along the winding direction, is smaller than a value obtained by multiplying the first distance by pi.